It depends on the group and their particular charism. Priests are not ordaied just to be ordained, a person can’t receive ordination like an honorary doctorate. Priests are ordained to serve the Church. If an older man was capable of fulfilling the ministry and charism of a particular order they would most likely consider him. If he was limited in his ability to fulfill those things then they most likely would not consider him.
There are also practical financial considerations. Older priests would, most likely, more quickly require more health care costs and care as they age. The religious order needs to be able to sustain those costs quicker than usual.
This, of course, is all on top of making sure the individual is a fit for the order’s spirituality and theology of common life.
